<!DOCTYPE html>
<html>
  <head>
    <title>
      计算器
    </title>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width"/>
  </head>
  <body>
      <input id="num1"/>
        *
      <input id="num2"/>
      <button onclick="jiSuan()">
        =
      </button>
      <input id="num3"/>
      <script>
        function jiSuan()
          {
            num3.value=num1.value*num2.value;
          }
      </script>

  </body>

</html>